In earth working or excavating the equipment used can be both large and expensive. It is preferred, therefore, that one piece of machinery perform several tasks. For example, breaking of the rock surface or over-burden, removal of soil, gravel, stones etc., land filling or soil replacement and levelling. Different tasks require different implements to be attached to the basic machinery so that each task may be efficiently performed. For example, the breaking up of stones or bitumen requires a jack hammer to be connected to the machinery. Similarly, movement of loose material such as soil, sand or gravel requires the use of a shovel or bucket. Finally, a fork means may be required for removal of large rocks or levelling of the land.
Earth working implements are usually pivotally connected to the dipper arm of the machinery and are articulatable about the end of the dipper arm by means of an appropriate linkage. In this way, the angle of incidence of the implement on the ground is adjustable and, in the case of a bucket or shovel, the implement may be rotated about the free end of the dipper arm to scrape or pick up and retain material.
Several different mechanisms for attaching the different implements to the earth working apparatus have been previously proposed. Virtually all, however, have disadvantages since they require precise control of the earth working apparatus in order to align apertures on the dipper arm and linkages with complementary apertures on the implement. A pin or axle is then usually inserted through these apertures to hold the implement in place.
This method is not only tedious and difficult to perform quickly, but requires all implements to be used on one machine to have matched aperture sizes and spacings to allow interchange of these implements.
The difficulties associated with attaching implements to the earth working machinery have led to the development of "quick-hitch" connections which allow for easier removal and/or replacement of the implement.
Previously proposed "quick hitch" systems have reduced the break out force applied by the implement to the earth due to an increase in the distance between the axis of rotation of the bucket and the free edge of the bucket.
Many previous "quick hitch" connections require that substantial changes or modifications be made to either the dipper arm and linkage or the implement which adds further inconvenience and cost.
For example, most previously proposed "quick-hitch" attachments are unsuitable for use with forked dipper arms. A forked dipper arm comprises a main strut with, usually, two parallel furcations or sub-struts extending from the main strut connected to the implement. These forked dipper arms are used to reduce twisting associated with the dipper arm when in use.
With single beam dipper arms, the "quick-hitch" connections must be placed on the outside of the dipper arm so as not to interfere with movement of the implement relative to the dipper arm. However, the placement of the "quick-hitch" connections on the outside of the dipper arm makes these connections liable to damage and additionally forces the operator to use an implement or bucket which is at least as wide as the outer periphery of the "quick-hitch" connections.
Such a "quick-hitch" attachment, designed for a single beam dipper arm, will simply not operate effectively on an earth working apparatus with a forked dipper arm since the adjustment mechanism will interfere with the furcations or sub-struts of the forked dipper arm.
Most "quick-hitch" connections also rely on some form of extendible members eg. mechanical or screw extenders or actuators, hydraulic rams etc. to clamp or hold the earth working implement on the dipper arm and linkage. While most equipment used for such "quick-hitch" connections is reliable, the sheer weight of the implement attached or loss of power to the clamping mechanism may result in detachment of the earth working implement from the dip arm and linkage with disastrous results.
Clearly there is a need for some form of attachment device which not only allows for easier and more rapid attachment of the implement to a forked dipper arm of an earth working apparatus but allows some latitude in the manufacture of different types of implements that may all be used on the same earth working apparatus, does not require any major alterations to the implement, and reduces the amount of damage caused to the attachment when used.
Further, there is a need for some form of safety device or back-up mechanism which ensures reliable connection of the earth working implement to the dip arm and linkage.
In an effort to ameliorate the disadvantages of the prior art it is proposed to provide a means of attachment of an implement to an earth working apparatus which offers a choice over the prior art and which, at least in the preferred embodiment, provides a method and means of attachment which is both easier and more rapid and reliable to use and manufacture while providing equivalent performance in its intended environment.